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Abstract

Purpose: Endothelial function and carotid intima-media thickness (IMT), are established markers of vascular aging. Aim of the study was to investigate the presence of early markers of atherosclerosis in rural Sherpa population of Kumbu Valley (Nepal), in comparison with lowlanders Caucasian subjects.

Results: High-altitude group presented higher heart rate and lower pulse pressure than sea-level group. FMD was also reduced (5.2±3.1 vs 6.8±3.0%, p=0.01), despite similar brachial artery diameter (3.7±0.6 vs 3.6±0.7 mm, p=0.64), and response to GTN (8.3±3.1 vs 7.6±2.2%, p=0.13). Conversely, IMT was lower in high altitude group than in the sea-level group (0.51 vs 0.61 mm, p<0.001). Sherpa people showed normal LV and RV systolic and diastolic function, PASP(28±6 mmHg) and PVR (0.16±0.4). In the overall population FMD (5.2±3.1%) was not correlated to O2 saturation (r=-0.03, p=0.74) and was similar in people with O2 saturation >90% and in those <90% (5.3 vs 5.0%, p=0.74). In the subgroup receiving O2 administration, FMD (from 3.1±2.5 to 3.8±2.6, p=0.46), response to GTN (from 8.9±2.7 to 8.7±1.9%), and echocardiographic parameters remained unchanged.

Conclusions: Endothelial function is reduced in healthy Sherpa high-altitude dwellers, in the presence of normal RV and LV function and pulmonary pressures, independently of cardiovascular risk factors and hypoxia. This finding is accompanied with a lower IMT and might represent a physiological adaptation to high altitude.